Displacement control valve for variable displacement compressor

ABSTRACT

The present invention provides a displacement control valve for a variable displacement compressor, the displacement control valve including a valve housing, in which a discharge chamber passage and a crank chamber passage are provided, and a valve body for opening and closing the valve, characterized in that a motor rotates the valve body to open and close the valve. Therefore, the present invention can reduce the overall length of the displacement control valve to reduce the size of the compressor, thereby achieving a compact structure of the compressor.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 2008-0099255, filed on Oct. 9, 2008, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to a displacement control valve for a variable displacement compressor and, more particularly, to a displacement control valve for a variable displacement compressor, which can reduce its overall length to reduce the size of the compressor, thereby achieving a compact structure of the compressor.

2. Discussion of Related Art

Since a compressor used in a refrigeration cycle of a vehicular air-conditioning system is directly coupled to an engine by a belt, the speed of the compressor cannot be controlled independently.

Therefore, a variable displacement compressor capable of changing the discharge volume of refrigerant to achieve an adequate cooling performance without restriction by the engine speed has been widely used recently.

Various types of variable displacement compressors such as the so-called swash plate type, rotary type, and scroll type compressors are used.

In the swash plate type compressor, a swash plate provided in a crank chamber such that the inclination angle of the plate is varied is rotated by the rotational movement of a rotating shaft, and a piston is reciprocated by the rotational movement of the swash plate. In this case, the refrigerant in a suction chamber is sucked into a cylinder by the reciprocating movement of the piston, compressed and discharged into a discharge chamber. At this time, the inclination angle of the swash plate is changed by a difference between the pressure in the crank chamber and the pressure in the cylinder, and thus the discharge volume of refrigerant is controlled.

Especially, an electronic solenoid type displacement control valve, which is actuated by an electric current, is adopted to control the pressure of the crank chamber such that the inclination angle of the swash plate is controlled, thereby controlling the discharge volume.

In this case, the displacement control valve is operated in such a manner that detection signals such as the rotational speed of the engine, the temperatures inside and outside the vehicle, and the temperature of an evaporator are calculated by a controller incorporating a CPU or the like and a control signal based on the calculated results is applied to an electromagnetic coil of the displacement control valve as an operating current.

A typical example of the displacement control valve for the variable displacement compressor is disclosed in U.S. Pat. No. 6,443,708 (hereinafter referred to as a “prior art”), and the schematic configuration thereof will be described with reference to FIG. 1 below.

As shown in the figure, the displacement control valve 20 for the variable displacement compressor in accordance with the prior art comprises a valve housing 40, a valve body 30, and an electromagnetic solenoid such that the valve body 30 is reciprocated as the electromagnetic solenoid is actuated by an electric current to open and close a discharge chamber passage 6 formed in the valve housing 40.

In the valve housing 40, a suction chamber passage 8 receiving the pressure of a suction chamber, a crank chamber passage 5 receiving the pressure of a crank chamber, and the discharge chamber passage 6 receiving the pressure of a discharge chamber of the compressor are provided. The discharge chamber passage 6 and the crank chamber passage 5 are connected to each other.

Moreover, the valve body 30 is reciprocated by the electromagnetic solenoid actuated by an electric current and passes through the crank chamber passage 5 during the reciprocating movement to open and close the discharge chamber passage 6. A spring 28 is provided at the bottom of the valve body 30 such that the valve body 30 descends during normal times when there is no external force to maintain the opened state of the discharge chamber passage 6.

The electromagnetic solenoid comprises a movable rod 24 connected to the valve body 30 and an electromagnetic coil 21 arranged on the circumference of the movable rod 24. A movable iron core 23 is provided at an end of the movable rod 24.

However, according to the prior art having the above-described structure, since the valve body 30 is configured to linearly reciprocate from the crank chamber passage 5, in which crank chamber pressure Pc acts, to the discharge chamber passage 6, in which discharge chamber pressure Pd acts, so as to open and close the crank chamber passage 5, the overall length of the displacement control valve 20 is increased, and thus the size of the compressor in which the displacement control valve 20 is installed is increased.

Moreover, there are problems that the manufacturing efficiency is degraded due to its complicated structure and configuration and the number of manufacturing processes is increased.

SUMMARY OF THE INVENTION

The prevent invention has been made in an effort to solve the above-described problems associated with the prior art, and an object of the present invention is to provide a displacement control valve for a variable displacement compressor, which can reduce its overall length to reduce the size of the compressor, thereby achieving a compact structure of the compressor.

Another object of the present invention is to provide a displacement control valve for a variable displacement compressor, which can simplify its structure to improve the manufacturing efficiency thereof.

Still another object of the present invention is to provide a displacement control valve for a variable displacement compressor, which can control the discharge volume using a balance of forces between a balance means and a motor.

According to an aspect of the present invention for achieving the above objects, there is provided a displacement control valve for a variable displacement compressor, the displacement control valve including a valve housing, in which a discharge chamber passage and a crank chamber passage are provided, and a valve body for opening and closing the valve, characterized in that a motor rotates the valve body to open and close the valve.

Preferably, the motor may be a stepping motor and the opening degree of the valve may be controlled by an input signal.

Preferably, a first discharge chamber passage of the valve housing and the crank chamber passage may be connected to each other, and a valve groove for controlling the opening degree between the first discharge chamber passage and the crank chamber passage may be formed in the valve body.

Preferably, the first discharge chamber passage may be formed to penetrate the center of the valve housing.

Preferably, the first discharge chamber passage may be formed to penetrate a portion of an upper part of the valve housing.

Preferably, the valve groove may be formed to penetrate the valve body in the longitudinal direction.

Preferably, the motor may be an induction motor in which the rotational torque is determined by an input current, and the displacement control valve may further include a balance means for applying a force to the valve body in an opening direction of the valve.

Preferably, the balance means may include: a movable groove formed in the valve housing; a movable projection formed in the valve body and inserted into the movable groove; and a spring inserted between the movable groove and the movable projection.

Preferably, the balance means may include: a second discharge chamber passage formed in the valve housing; a suction chamber passage formed in the valve housing; and first and second pressure grooves formed in the valve body to correspond to the second discharge chamber passage and the suction chamber passage, respectively.

Preferably, an off-spring may be inserted between the second discharge chamber passage and the first pressure groove.

Preferably, an off-spring may be interposed between a centering groove formed in the valve housing and the valve body.

Preferably, a spring may be inserted between the bottom of the valve housing and the bottom of the valve body.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal cross-sectional view showing the structure of a displacement control valve in accordance with a prior art;

FIG. 2 is a longitudinal cross-sectional view showing the structure of a variable displacement compressor in accordance with the present invention;

FIG. 3A is a longitudinal cross-sectional view showing the structure of a displacement control valve in accordance with a first embodiment of the present invention;

FIG. 3B is a longitudinal cross-sectional view showing a closed state of FIG. 3A;

FIG. 4 is a plan view of FIG. 3A;

FIG. 5 is a plan view showing the structure of a displacement control valve in accordance with a second embodiment of the present invention;

FIG. 6 is a plan view showing the structure of a displacement control valve in accordance with a third embodiment of the present invention;

FIG. 7A is a longitudinal cross-sectional view taken along line I-I of FIG. 6; and

FIG. 7B is a longitudinal cross-sectional view taken along line II-II of FIG. 6.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings such that those skilled in the art to which the present invention pertains can easily practice the present invention.

First, the structure of a swash plate type variable displacement compressor including a displacement control valve in accordance with the present invention will be schematically described with respect to FIGS. 2 to 4.

FIG. 2 is a longitudinal cross-sectional view showing the structure of a swash plate type variable displacement compressor in accordance with the present invention, FIG. 3A is a longitudinal cross-sectional view showing the structure of a displacement control valve in accordance with a first embodiment of the present invention, FIG. 3B is a longitudinal cross-sectional view showing a closed state of FIG. 3A, and FIG. 4 is a plan view of FIG. 3A.

As shown in the figures, a swash plate type variable displacement compressor C comprises a cylinder block 110 having a plurality of cylinder bores 112 arranged in parallel in a longitudinal direction on its periphery, a front housing 116 air-tightly connected to the front of the cylinder block 110, and a rear housing 118 air-tightly connected to the rear of the cylinder block 110 with a valve plate 120 interposed therebetween.

A crank chamber 186 is provided in the front housing 116. One end of a drive shaft 144 is rotatably supported around the center of the front housing 116, and the other end of the drive shaft 144 passes through the crank chamber 186 and is supported by a bearing provided in the cylinder block 110.

Moreover, a lug plate 154 and a swash plate 150 are provided around the circumference of the drive shaft 144 in the crank chamber 186.

A pair of support arms 162 for transmitting power, each having a guide hole 164 formed to penetrate its center, are formed to protrude from one side of the lug plate 154 and a ball 166 is formed on one side of the swash plate 150 such that the ball 166 of the swash plate 150 is slidably moved in the guide hole 164 of the lug plate 154 by the rotation of the lug plate 154 to change the inclination angle of the swash plate 150.

Moreover, a plurality of pistons 114 are slidably inserted into the outer circumferential surface of the swash plate 150 with a shoe 176 interposed therebetween.

Therefore, the pistons 114 inserted into the outer circumferential surface of the swash plate 150 with the shoe 176 interposed therebetween are reciprocated in each of the cylinder bores 112 of the cylinder block 110 by the rotation of the inclined swash plate 150.

A suction chamber 122 and a discharge chamber 124 are formed in the rear housing 118, and a suction port 132 and a discharge port 136 are formed in the valve plate 120, interposed between the rear housing 118 and the cylinder block 110, in a position corresponding to each of the cylinder bores 112.

Refrigerant of the suction chamber 122 is sucked into the cylinder bores 112 by the reciprocating movement of the pistons 114, compressed and discharged into the discharge chamber 124. At this time, the inclination angle of the swash plate 150 is changed by a difference between the pressure in the crank chamber 186 and the pressure in the cylinder bore 112, and thus the discharge volume of refrigerant is controlled.

In detail, the variable displacement compressor in accordance with the present invention employs a displacement control valve 200 to be opened and closed by an electric current such that the pressure of the crank chamber 186 is controlled and the inclination angle of the swash plate 150 is adjusted, thus controlling the discharge volume.

A displacement control valve in accordance with a first embodiment of the present invention will now be described with reference to FIGS. 3A, 3B, and 4.

As shown in the figures, the displacement control valve 200 in accordance with the first embodiment of the present invention comprises a valve housing 210 having a pair of upper and lower housings, a valve body 220 rotatably mounted in the valve housing 210, and a motor 230 axially connected to the valve body 220 to transmit a drive force.

A crank chamber passage 211 in which pressure Pc of the crank chamber 186 acts and a first discharge chamber passage 212 in which pressure Pd of the discharge chamber 124 acts are provided in the valve housing 210. The crank chamber passage 211 and the first discharge chamber passage 212 are connected to each other by the rotation of the valve body 220.

Moreover, the first discharge chamber passage 212 is formed at the top of the valve housing 210, and the crank chamber passage 211 is formed perpendicularly to the side of the valve housing 210.

Meanwhile, the first discharge chamber passage 212 may be formed to penetrate the center of the valve housing 210 as shown in (a) of FIG. 4 or may be formed to penetrate a portion of the upper of the valve housing 210 as shown in (b) of FIG. 4.

The valve body 220 is closely adhered to the top of the valve housing 210 and includes a valve groove 221 formed on one side of the valve body 220 to control the opening degree between the first discharge chamber passage 212 and the crank chamber passage 211.

The valve groove 221 may be formed to penetrate the valve body 220 in the longitudinal direction or may be configured in the form of a groove from which a portion is removed as shown in the figures. Moreover, it is sufficient that the valve groove 221 has a structure which can connect the crank chamber passage 211 to the discharge chamber passage 212, and there is no necessity to limit the shape of the valve groove 221.

Therefore, as an electric current is applied to the motor 230 comprising a stator 231 and a rotor 232, the valve body 220 is rotated such that the first discharge chamber passage 212 formed in the valve housing 210 is opened and closed by the valve groove 221.

Meanwhile, the motor 230 comprises a stepping motor which is rotated by a predetermined angle in response to a pulse signal and, since this stepping motor is well known in the art, its detailed description will be omitted.

Moreover, it is preferable that a spring (not shown) is provided at the bottom of the valve body 220 such that the top of the valve body 220 is closely adhered to the inside of the valve housing 210, thus preventing the discharge pressure from leaking.

Next, the operation of the displacement control valve in accordance with the first embodiment of the present invention will be described with reference to the drawings.

First, in the initial state, the power supply to the displacement control valve 200 is cut off and, in this state, the valve groove 221 of the valve body 220 connects the first discharge chamber passage 212 and the crank chamber passage 211 and maintains the opened state (refer to FIG. 3A).

Here, the motor 230 is a stepping motor and the valve groove 221 is located in a position that connects the first discharge chamber passage 212 and the crank chamber passage 211 during power supply cut-off.

Therefore, since the discharge pressure Pd passes through the first discharge chamber passage 212 and the crank chamber passage 211 and acts on the crank chamber 186, the pressure of the crank chamber 186 is increased and the inclination angle of the swash plate 150 is rapidly reduced, thereby reducing the discharge volume of refrigerant.

Then, when detection signals such as the rotational speed of an engine, the temperatures inside and outside a vehicle, and the downstream temperature and pressure of an evaporator are applied to a motor control unit (MCU), the MCU calculates a thermal load based on the detection signals and, if the calculated thermal load exceeds a predetermined value, a current signal for increasing the discharge volume of refrigerant is applied to a power source.

Accordingly, an increased current flows through the motor 230 to rotate the motor 230 and, at the same time, the valve body 220 connected to the motor 230 is also rotated, thereby closing the first discharge chamber passage 212 or the crank chamber passage 211.

As a result, the pressure in the crank chamber 186 is reduced and the inclination angle of the swash plate 150 is increased, thus rapidly increasing the discharge volume and pressure of the compressor.

Meanwhile, although the above description refers to the first discharge chamber passage 212 which is completely opened or closed, the discharge volume and pressure of the compressor can be readily adjusted since the opening degree between the first discharge chamber passage 212 and the crank chamber passage 211 is determined by the current value input to the stepping motor 230.

Next, displacement control valves in accordance with second and third embodiments of the present invention will be described, in which the same elements as those of the first embodiment are designated by the same reference numerals, and their detailed description will be omitted.

FIG. 5 is a plan view showing the structure of a displacement control valve in accordance with a second embodiment of the present invention, FIG. 6 is a plan view showing the structure of a displacement control valve in accordance with a third embodiment of the present invention, FIG. 7A is a longitudinal cross-sectional view taken along line I-I of FIG. 6, and FIG. 7B is a longitudinal cross-sectional view taken along line II-II of FIG. 6.

First, each of the displacement control valves 200′ and 200″ in accordance with the second and third embodiments of the present invention is configured in the same manner as the displacement control valve 200 of the first embodiment. That is, each of the displacement control valves 200′ and 200″ comprises a valve housing 210 in which a first discharge chamber passage 212 and a crank chamber passage 211 are connected to each other, a valve body 220 including a valve groove 221 configured to rotatably open and close the first discharge chamber passage 212, and a motor 230 for transmitting drive power to the valve body 220.

However, a typical induction motor is used as the motor 230 in the second and third embodiment of the present invention, and the valve groove 221 rotatably opens and closes the first discharge chamber passage 212 by the rotation of the motor 230.

Meanwhile, since the motor 230 is an induction motor which is rotated when an electric current is applied thereto in a manner different from the stepping motor which is rotated by a predetermined angle in response to a pulse signal, it is necessary to regulate the rotation range.

Therefore, a balance means 240 for applying a rotational force proportional to the rotational force of the motor 230 in the opposite direction is further provided.

FIG. 5 shows the displacement control valve 200′ in accordance with the second embodiment, in which the balance means 240 comprises a movable groove 241 formed in the valve housing 210, a movable projection 242 formed in the valve body 220 and inserted into the movable groove 241, and a spring 243 inserted between the movable groove 241 and the movable projection 242.

Meanwhile, although the balance means 240 is formed at the top of the valve housing 210 in FIG. 5, the present invention is not limited thereto, and the balance means 240 may be formed at the bottom of the valve housing 210.

Therefore, when no electric current is applied to the motor 230, the first discharge chamber passage 212 and the crank chamber passage 211 are opened by the valve groove 221 due to the elastic force of the spring 243. When an electric current is applied to the motor 230, the motor 230 is rotated and, at the same time, the valve body 220 is rotated, thereby closing the first discharge chamber passage 212 or the crank chamber passage 211.

At this time, the spring 243 applies a rotational force F₁ to the valve body 220 in a direction that opens the first discharge chamber passage 212 and the motor 230 applies a rotational force F₂ corresponding to the rotational force F₁ of the spring 243 based on the amount of current applied to the motor 230, thereby controlling the rotation of the valve body 220. As a result, it is possible to change the discharge volume and pressure of the compressor by controlling the opening degree between the first discharge chamber passage 212 and the crank chamber passage 211.

Meanwhile, FIGS. 6 and 7 show the displacement control valve 200″ in accordance with the third embodiment, in which a balance means 240 comprises a second discharge chamber passage 241 formed in the valve housing 210, a suction chamber passage 242 formed in the valve housing 210, and first and second pressure grooves 243 and 244 formed in the valve body 220 to correspond to the second discharge chamber passage 241 and the suction chamber passage 242, respectively.

Here, discharge pressure Pd by the second discharge chamber passage 241 is applied to the first pressure groove 243 to rotate the valve body 220 in a direction that opens the first discharge chamber passage 212, and suction pressure Ps by the suction chamber passage 242 is applied to the second pressure groove 244 to rotate the valve body 220 in a direction that closes the first discharge chamber passage 212.

As a result, the discharge pressure Pd is higher than the suction pressure Ps, and thus the rotational force F₁ is applied to rotate the valve body 220 in a direction that opens the first discharge chamber passage 212.

On the contrary, the motor 230 applies the rotational force F₂ proportional to the amount of current applied to the motor 230 to rotate the valve body 220 in a direction that closes the first discharge chamber passage 212.

Moreover, an off-spring 245 is inserted between the second discharge chamber passage 241 and the first pressure groove 243.

The installation position of the off-spring 245 is not limited to the space between the second discharge chamber passage 241 and the first pressure groove 243 and may be interposed between a centering groove 213 formed in the valve housing 210 and the valve body 220.

Therefore, when no electric current is applied to the motor 230, the first discharge chamber passage 212 is opened by the valve groove 221 due to the elastic force of the spring 243. When an electric current is applied to the motor 230, the motor 230 is rotated and, at the same time, the valve body 220 is rotated, thereby closing the first discharge chamber passage 212 or the crank chamber passage 211.

At this time, the discharge pressure Pd and the suction pressure Ps act on the first and second pressure grooves 243 and 244, respectively, to apply the rotational force F₁ for rotating the valve body 220 in a direction that opens the first discharge chamber passage 212 and the motor 230 applies the rotational force F₂ corresponding to the rotational force F₁ based on the amount of current applied to the motor 230, thereby controlling the opening degree of the valve. Therefore, it is possible to change the discharge volume and pressure of the compressor.

As a result, the opening degree of the valve is determined by the balance between the rotational force F₁, obtained by subtracting the suction pressure Ps value from the discharge pressure Pd value, and the rotational force F₂ of the motor 230, which is determined in proportion to the amount of current applied to the motor 230.

As described above, according to the displacement control valve for the variable displacement compressor of the present invention, it is possible to reduce the overall length of the displacement control valve to reduce the size of the compressor, thereby achieving a compact structure of the compressor.

Moreover, it is possible to simplify the structure of the displacement control valve, thereby improving the manufacturing efficiency thereof.

Furthermore, it is possible to control the discharge volume using a balance of forces between the balance means and the motor.

It will be apparent to those skilled in the art that various modifications can be made to the above-described exemplary embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers all such modifications provided they come within the scope of the appended claims and their equivalents. 

1. A displacement control valve for a variable displacement compressor, the displacement control valve comprising a valve housing, in which a discharge chamber passage and a crank chamber passage are provided, and a valve body for opening and closing the valve, characterized in that a motor rotates the valve body to open and close the valve.
 2. The displacement control valve of claim 1, wherein the motor is a stepping motor and the opening degree of the valve is controlled by an input signal.
 3. The displacement control valve of claim 2, wherein a first discharge chamber passage and the crank chamber passage of the valve housing are connected to each other and a valve groove for controlling the opening degree between the first discharge chamber passage and the crank chamber passage is formed in the valve body.
 4. The displacement control valve of claim 3, wherein the first discharge chamber passage is formed to penetrate the center of the valve housing.
 5. The displacement control valve of claim 3, wherein the first discharge chamber passage is formed to penetrate a portion of an upper part of the valve housing.
 6. The displacement control valve of claim 3, wherein the valve groove is formed to penetrate the valve body in the longitudinal direction.
 7. The displacement control valve of claim 1, wherein the motor is an induction motor in which the rotational torque is determined by an input current and the displacement control valve further comprises a balance means for applying a force to the valve body in an opening direction of the valve.
 8. The displacement control valve of claim 7, wherein a first discharge chamber passage of the valve housing and the crank chamber passage are connected to each other and a valve groove for controlling the opening degree between the first discharge chamber passage and the crank chamber passage is formed in the valve body.
 9. The displacement control valve of claim 8, wherein the first discharge chamber passage is formed to penetrate the center of the valve housing.
 10. The displacement control valve of claim 8, wherein the first discharge chamber passage is formed to penetrate a portion of an upper part of the valve housing.
 11. The displacement control valve of claim 8, wherein the valve groove is formed to penetrate the valve body in the longitudinal direction.
 12. The displacement control valve of claim 7, wherein the balance means comprises: a movable groove formed in the valve housing; a movable projection formed in the valve body and inserted into the movable groove; and a spring inserted between the movable groove and the movable projection.
 13. The displacement control valve of claim 7, wherein the balance means comprises: a second discharge chamber passage formed in the valve housing; a suction chamber passage formed in the valve housing; and first and second pressure grooves formed in the valve body to correspond to the second discharge chamber passage and the suction chamber passage, respectively.
 14. The displacement control valve of claim 13, wherein an off-spring is inserted between the second discharge chamber passage and the first pressure groove.
 15. The displacement control valve of claim 13, wherein an off-spring is interposed between a centering groove formed in the valve housing and the valve body.
 16. The displacement control valve of claim 1, wherein a spring is inserted between the bottom of the valve housing and the bottom of the valve body. 